420 



PART II. 



REVIEWS. 



Art. I. Cours de VHistoire Naturelle des Mammiferes, Par M. 

 Geoffroy Saint-Hilaire. Paris, 1829. 1 vol. 8vo. 



This work contains the lectures which its celebrated author 

 delivered, in 1828, at the Jardin du Roi. They were pub- 

 lished separately immediately after their delivery, not with the 

 permission merely, but under the superintendence of the Pro- 

 fessor, to satisfy, as he tells us, the eager longings of the 

 Parisians after useful knowledge; and have none of those 

 inaccuracies which disfigure the lectures reported in the heb-» 

 domadal periodicals of our own country. 



A principal object of the author is to defend and illustrate 

 a theory of animal organisation which properly originated 

 with him, and of which he continues to be the most able ad- 

 vocate. The theory is, that all animals are constructed after 

 one model, or, in other words, the organisation of them may 

 be reduced to a uniform type ; so that every part which is 

 found in each class has an analogous part in the other classes. 

 It is admitted that the parts considered analogous in two ani- 

 mals somewhat distant in the scale of being are apparently 

 very dissimilar in form, and are appropriated to seemingly 

 different functions ; but, on attentive examination, intermediate 

 forms appear, and the one slides insensibly into the other^ 

 every change bringing with it a corresponding modification 

 of the uses of the part. All the bones, for example, in the 

 cranium correspond to one another in all animals which have 

 a cranium; not in figure or proportions, for in that they 

 obviously differ ; nor in use, for a slight alteration of form is 

 often accompanied with a change in function ; but they are 

 analogous in number, and essentially in position and structure. 

 Thus, by comparing the foetal head of a quadruped with that 

 of a reptile, Saint-Hilaire discovers relations in the number 

 and arrangement of the component pieces, which were not 

 previously perceived. In the same manner, the os quadratum 

 in birds is proved to be analogous to the tympanum of the 

 mammalia ; and the bony or scaly appendages to the branchiae 

 of fish, which are known by the general name of opercula, 

 and are concerned in the mechanism of the respiration of 



